A friend of mine uses an adapter like this to have ethernet available all over his house. He uses a different model, but the idea is the same. Robert Heron recommended this model so for $34 it seemed like a steal.

The idea is to attach one to your router and plug it into an electrical outlet. Don’t use a power strip adapter. You plug the other one into the outlet where you want the new ethernet. You press a button on one adapter and then go down to the second adapter and press the button on it. It then connects and you are on the internet.